I've had pretty good luck using the free S2 Calendar Widget by Futaba. I found it on the Market about a month ago and have used it ever since. It has 2x1, 2x2, & 3x3 widgets and a fair amount of settings to customize. It's not real fancy but you can create events and see your calendar in 1-day, 1-week, and 1-month formats as well as "agenda" which is a vertical listing of upcoming events. It's rated 4.5, it's ad free, and it's free of charge.

I think his question was more along the lines of an actual calendar and NOT a calendar widget/alternate.

I personally use the regular calendar, which DOES sync up with your gmail account. Although I've hear that gmail only keeps record of 60 days, or something like that, maybe someone can shine a bit more light on that